text:
What does it mean "the airport has the code A 129" (Nida airport, Europe)?
It has been announced that Nida airport (Lithuania) officially opens again and obtains the code "A 129" (here). The source does not say that kind of code it is and what does it mean. Would it be possible to clarify? Is it a place designation, or the airport category?
Nida airport has been closed for many years. It is not very tiny, passenger planes used to land there many years ago. Recently it has been reopened for very small planes while probably something bigger would be able to land there as well. Basically this rather long runway has the status of untowered airstrip.
Nida airport has ICAO code EYND and no IATA code.

I can't find any information on it (the Lithuanian CAA site doesn't have published regulations, at least not in English) but I'm guessing that its a class of aircraft operations that are allowed on the airport.

I tried to find such information myself. There is little to none recent information about the airport as it has been closed for many years. I just wanted to as if A 129 tells maybe something to somebody immediately.

@ymb1: Ok. There is a bit of information here.

This is really just an educated guess, but it sounds like it was assigned that identifier by the Lithuanian civil aviation authority. It obviously didn't warrant an IATA code. Since it was closed to most traffic the ICAO code may not have been in use. The wiki page said it was just considered an "airstrip," so it was assigned an ID by the government. (It also mentioned lack of fuel service. That might be a requirement for an ICAO registration. I don't know.)
Here in the US large airports will have an IATA CODE, an ICAO code and an FAA location ID. [example: O'Hare airport - IATA: ORD - ICAO: KORD - FAA: ORD] A small GA airport won't merit an IATA or ICAO code but it will have an FAA location ID. The small airport near where I work has no IATA or ICAO code. It has the FAA location identifier K68.

USA has more small airports than most other places. In Europe even the smallest air strips generally do have ICAO codes.


text:
What would be the stall speed of Solar Impulse?
In most of the tables, only the take off (22 mph) and cruise (43) speed of the Solar Impulse are listed. It is an experimental plane, slow, with very huge wing for solar batteries.
The take off speed may not be the slowest speed the aircraft can fly, for instance, when landing. Is it possible to infer somehow the expected slowest speed of this airplane?

Solar Impulse has no flaps and a high aspect ratio wing. Therefore, the c$_{l_{max}}$ of the wing should be no higher than 1.8, most likely 1.6. While a rigid airfoil can be designed with a higher c$_{l_{max}}$, it will not have an attractive L/D and a shorter wing would have a c$_{l_{max}}$ below that of the airfoil. Since no fuel is consumed, mass is constant, which makes it very easy to give a lower bound for the minimum speed.
Solar Impulse 2 has 269.5 m² wing area to carry its 2.3 tons of mass. This is a wing loading of just 8.53 kg/m². If we assume standard day conditions at sea level (density $\rho$ = 1.225 kg/m³), we find vor v$_{min}$:
$$v_{min} = \sqrt{\frac{2\cdot m\cdot g}{c_{l_{max}}\cdot S\cdot \rho}} = 9.24 \;\small{\frac{m}{s}} \;\text{or}\; 33.27\; \small{\frac{km}{h}}$$
For those of you from metrically challenged cultures: This is 18 knots or 20.67 mph.

So very close to take off speed. I assume this is because it has no flaps or anything else to configure it differently for landing.

@h22: Exactly right. It is a one-point design.

The root is rather the absence of fuel, isn't it? If you need the same lift for take-off and landing (because same weight) then you don't need a different configuration. it could have flaps to adapt cruise/low speed. But even if it had flaps, it would use the same flap configuration for landing and take-off.

@SylvainBoisse: No, look at gliders, ASW-20 or ASH-25 for example. They also don't change mass during a flight (OK, except for water ballast) and profit immensely from flaps. They have a setting for slow flight and one for landing. The slow setting is usually used for takeoff, but never the landing setting because it creates too much drag. The root is that Solar Impulse flies at one speed mostly, just above stall.

@PeterKämpf Good point. I've never looked much into gliders, but you're right they are the closest thing to an electric plane. I'll look into this on SO. Thank you

Thanks for taking care of those of us who are metrically challenged! :)

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text:
What is the meaning of HOT-1, HOT-2, CAM, etc., in cockpit voice recorder transcripts?
When reading the the written down recordings of CVR like here, for instance, it is common to see abbreviations like HOT-1, HOT-2 or CAM. I guess that CVR records multiple channels and the codes indicate the microphone that is believed to be closest to the source of the sound. But what exactly these abbreviations mean? Which others are possible?

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text:
How serious is the problem of "stopping too far" next to the jet bridge?
In the answer to the recent question "How does an airliner adjust ...", there is the mentioning of the signal: "STOP TOO FAR". But what to do if you see this?
In other words, if the airliner stops too far next to the jet bridge, how is this problem typically resolved? I was thinking about the possible approaches:

In my car, I would just drive backwards. But seems that the usage of the reverse thrust is somewhat frowned upon.
The aircraft will be serviced without the jet bridge (movable stairs, etc).
The aircraft will be towed backwards where it should be.
The jet way most often can be adjusted to compensate the unexpected location, the sign is just the warning.
No ATPL holder would ever make a mistake of this kind anyway.

Also, how often does this happen? Is this a very rare problem or something more common?

Wouldn’t using reverse thrust (or any thrust) in the jetway area be a hazard to the grounds crew as well as the vast amount of glass in the area?

I can't tell you how often it happens, but the procedure is quite simple: stop the aircraft immediately, and alert the ground crew. It is then up to the ground crew to decide what, if anything, needs to happen. If the aircraft has just slightly passed the intended stop position, maybe it can just stay where it is. If it has overshot significantly, it may be required to push the aircraft back to the correct position with a tug. Worst case, the aircraft might have actually hit some obstacle (building, vehicle, jet bridge) in which case the aircraft or surrounding equipment might have been damaged.

This does happen. Despite what they'd like you to believe airline pilots are mere mortals, so they occasionally overshoot. Ground crews can mess up instructions as well. I've seen it happen once on a flight I was on, the pilot announced there'd be a short delay because they overshot the gate, in the end there was just enough width on the jetway to accommodate. I have no statistics on it, all I can say is it's rare.
Some jetways have the capacity to move left and right as well as forward and back, an overshoot in this case would likely be no problem unless it was so far in it was out of movement limits. These days most jetways I've seen can only move forward and back, so accurate braking is more critical, if a jet overshoots too far it will need a pushback to align it. Of course rolling stairs could also be used on rear doors, but it's hard to see that being used as it means a lot more messing around.

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Has the number of angle of attack sensors been reduced in Boeing 737 Max, in comparison to the older models?
Boeing 737 is flying since 1967. I would like to know first how many ' angle of attack sensors' does it have, and has they number been reduced for Boeing 737 Max, in comparison to the older models like 737 Next Generation or 737 Classic, for instance?

There is already an answer on here about how many the B737 MAX have (the answer is 2), and I've found this Airworthiness Directives which states somewhere far down:

Do a general visual inspection of the left and right angle of attack (AOA) sensor as applicable, to determine if a certain AOA sensor with a paddle type vane is installed[...]

This brings me to the conclusion that there always have been 2 AOA sensors on the B737, as this Airworthiness Directive is dated to 2012. (To be fair, at least since then there have always been 2 AOA sensors).
As a decrease in the amount of AOA sensors from 1967 to 2012 seems unlikely to me, I'd say there are and always have been only 2 sensors on the B737. Following that train of thoughts, the amount of sensors has thus not changed with the different versions of the B737
Interesting sidenote: The AD is valid not only for B737 but also affects all kinds of 727 and 747 models, which indicates that they also have 2 sensors only, but doesn't necessarily mean that other Boeing aircraft have more!


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Is a braking rotation immediately after touching down a known maneuver?

In this video the airliner landing on grass rotates high up after touching down, looks like more than it would do during take off. Is it a known possible way to drop the speed or it was more for the show? Is this maneuver ever used during more conventional landings?

Maybe it keeps the wheels from sinking in soft ground at high speed?

That aircraft is an Ilyushin Il-62 by Interflug, which was landed there by Heinz-Dieter Kallbach. It is now a museum.

There was a bit of a bounce and skip at touchdown along with the nosewheel bouncing due to the uneven ground and aggressive landing.  He was probably doing it to hold the nosewheel off after the bounce, to reduce the main wheel contact force somewhat (the normal soft field landing technique) but it looks to me like he overcontrolled with the pitch a bit.
There will be relatively little braking friction so initially you would get better deceleration with the high pitch attitude, but that benefit declines quickly as you slow down and you quickly become reliant on braking and reversers (If the grass is wet, you have about as much braking as compacted, glazed snow, that is, not much; they would have to makes sure the ground was dry or he would have slid into the next field).
If you're on pavement, you want maximum braking as soon as possible, which means you want the lift dumpers out as soon as possible, so you wouldn't use that sort of technique; it's just get the mains on, then fly the nosewheel on, then hard on the brakes right away.  You'd have a longer landing run on pavement trying to land like that, plus there's too much risk of bouncing the whole thing back in the air just as the lift dumpers are extending or about to extend, which results in follow-on touchdown that will rattle teeth and blow tires.

The screenshot in the question looks like the spoilers are out (which prevents them from lifting off again, I suppose).

I watched it again and you're right they come out right away, maybe because the nosewheel touched and the logic was satisfied, or as I suspect, the airplane is Russian and has manually deployed lift dumpers with the copilot ready on the switch.  There was a CRJ landing a while back where there was a large bounce and the pilot advanced the thrust then changed his mind and pulled them back, while the "on-ground" logic was still active.  The lift dumpers came out when the thrust levers were pulled, while about 15 ft in the air and it free-fell to the ground and collapsed the main gear.


text:
Where is RC aircraft flying allowed in the US?
In the US, where are you allowed to fly RC aircraft? AMA says you should stay away from airports and below 400 feet. Is there any actual law about this?
I'm guessing you are free to fly on your own property. How about other places? Does it have to be an actual RC field? Can it be a park, as long as you don't endanger anyone?
If this varies with local rules, is there some reference for finding more information about which areas allow/disallow it?

Regulations have changed greatly since this question was asked and since the last answer was posted. For example, there is not longer a requirement to contact the airport or control tower when flying within 5 miles of an airport, but there is a requirement to use the LAANC system to get "prior authorization" before flying in most controlled airspace. There is also a blanket maximum 400' AGL altitude limi

Update
Everything in the second section (my original answer) used to be true (well, except for the first statement), but doesn't consider that the FAA Modernization and Reform Act of 2012 made this regulatory.
The FAA has a webpage that discuss it in more detail , but here is an image that covers the basics:

There is also a much more detailed letter of interpretation from the FAA which discusses their ability to enforce the regulation and many other parts of 14 CFR 91 if a model aircraft endangers another aircraft, flies within 5 miles of an airport without receiving a clearance, flies into a restricted area, etc.

The short version is that it isn't regulated (yet).  For more details, read on.
FAA has an Unmanned Aircraft (UAS) Questions and Answers page on their website which addresses this:

Do I need permission from the FAA to fly a UAS for recreation or as a hobby?
There are two ways for recreational or hobby UAS fliers to operate in the National Airspace System in accordance with the law and/or FAA regulations.
...
Option #1. Fly in accordance with the Special Rule for Model Aircraft (Public Law 112-95 Section 336). Under this rule, operators must:
Fly for hobby or recreational purposes only
Follow a community-based set of safety guidelines
Fly the UAS within visual line-of-sight
Give way to manned aircraft
Provide prior notification to the airport and air traffic control tower, if one is present, when flying within 5 miles of an airport
Fly UAS that weigh no more than 55 lbs. unless certified by a community-based organization
Register the aircraft (UAS over 0.55 lbs. and less than 55 lbs. can be registered online at registermyuas.faa.gov; UAS 55 lbs. or greater must be registered through the FAA's paper-based process)

The other option is to obtain a pilot certificate and comply with part 107 UAS regulations.
The FAA has also published an Advisory Circular Model Aircraft Operating Standards, which states:

1 - PURPOSE. This advisory circular (AC) provides guidance to persons operating Unmanned Aircraft (UA) for hobby or recreation purposes meeting the statutory definition of “model aircraft” contained in Section 336 of Public Law 112-95, the FAA Modernization and Reform Act of 2012. This AC describes means by which model aircraft may be operated safely in the National Airspace System (NAS). Nothing in this AC changes the requirement to comply with the statute or any applicable regulations.
...
6 - MODEL AIRCRAFT OPERATIONS.
...
b. Model Aircraft Hazards in the NAS. While aero-modelers generally are concerned about safety and exercise good judgment when flying model aircraft for the hobby and recreational purposes for which they are intended, they may share the airspace in which manned aircraft are operating. Unmanned aircraft, including model aircraft, may pose a hazard to manned aircraft in flight and to persons and property on the surface if not operated safely. Model aircraft operations that endanger the safety of the National Airspace System, particularly careless or reckless operations or those that interfere with or fail to give way to any manned aircraft may be subject to FAA enforcement action.
c. Determination of “Model Aircraft” Status. Whether a given unmanned aircraft operation may be considered a “model aircraft operation” is determined with reference to section 336 of Public Law 112-95:
(1) The aircraft is flown strictly for hobby or recreational use;
(2) The aircraft operates in accordance with a community-based set of safety guidelines and within the programming of a nationwide community-based organization (CBO);
(3) The aircraft is limited to not more than 55 pounds, unless otherwise certified through a design, construction, inspection, flight test, and operational safety program administered by a CBO;
(4) The aircraft operates in a manner that does not interfere with, and gives way to, any manned aircraft; and
(5) When flown within 5 miles of an airport, the operator of the model aircraft provides the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport) with prior notice of the operation. Model aircraft operators flying from a permanent location within 5 miles of an airport should establish a mutually agreed upon operating procedure with the airport operator and the airport air traffic control tower (when an air traffic facility is located at the
  airport).
d. Public Law 112-95 recognizes the authority of the Administrator to pursue enforcement action against persons operating model aircraft who endanger the safety of the National Airspace System. Accordingly, model aircraft operators must comply with any Temporary Flight Restrictions (TFR).
...
Model aircraft must not operate in Prohibited Areas, Special Flight Rule Areas or, the Washington National Capital Region Flight Restricted Zone, without specific authorization.
e. Model aircraft operators should follow best practices including limiting operations to 400 feet above ground level (AGL).
f. All other operators and for additional information on Unmanned Aircraft Systems please visit: http://www.faa.gov/uas/ .

Note that this is "guidance" and recommended procedures that the FAA "encourages voluntary compliance with" in order to "reduce the potential for hazards and create a good neighbor environment with affected communities and airspace users."
That being said, any city/county/state could have rules on their books, but there is not national guidance for this.

Although it does not specifically regulate model aircraft, being familiar with FAR 101 (which covers balloons, kites, and model rockets) and keeping within those restrictions is probably a good idea as well. (The AC above largely mirrors FAR 101.)

Those standards are actually from the AMA - http://www.modelaircraft.org/ - and in general, we don't agree that the FAA has any regulatory power over us. However, we want to fly safely and generally agree with the rules.

@Jasmine It seems pretty clear to me with the new rules, but definitely was that way in the past (hence my answer being in two parts).  If you have any reference to support your position, by all means please post an answer explaining why you don't agree that the FAA has any regulatory power....

It's already mentioned in your answer, but you kinda have it backwards. The FAA Modernization and Reform Act of 2012 specifically states that the FAA has no regulatory power over model aircraft operations (the infamous "section 336").

@Jasmine Oh, I thought that you were disagreeing with my answer, lol.  Yes, according to that act, RC airplanes are not covered by the authority of the FAA as long as the mentioned provisions are met.  If someone is doing something contrary to that act though, they would be covered.

@Lnafziger This FAA link is broken.

General American law: it's legal if it ain't illegal. And there's no overarching law that covers all RC airplanes. So the law is you can fly them except where you can't. That may sound unhelpful, but my point is that unless where you are has specific laws or rules against it, you're fine. There's also a general restriction on commercial use.
What many people don't know about is Temporary Flight Restrictions(TFRs). TFRs happen all over the country for all sorts of reasons, and they are just what they sound like: a temporary restriction on flying over a certain area. They could be for wildfires, or large events, or VIPs. When the President of the US travels, there is usually a 30 mile radius TFR put up around the area.
The reason I bring this up is these TFRs almost always include "no RC airplanes" as a restriction. So the President visits a city 25 miles away, you fly your RC airplane in your backyard, and you're technically breaking federal law.

I broke that federal law yesterday. The truth of the matter about TFRs is we really don't care (and quite often don't know either). We are responsible adults, and we aren't a threat to the president, or to any full scale traffic in any way. Same way people speed on the highway, they will ignore these stupid laws too.

The short answer is: commercial flights (money is involved) are almost always illegal. Hobby flights (no $) are not controlled by very many binding laws, but "strong guidance" is given in the above poster, including 1) not over groups of people, not near airports, etc., and (more controversial) always below 400 feet. The legal basis for the statement that you "must follow safety guidelines" does not exist. People in my club go out in the desert and fly several thousand feet high, for example. But they would never do that at our regular field, because they know it is stupid, unsafe, and will upset the local helicopters!
  This is a very controversial and evolving area. The FAA is attempting to assert much greater de-facto jurisdiction, for example by proposing a definition that on paper might regulate unpowered balsa wood aircraft. It is pretty clear that the FAA has the right to forbid commercial flights, although a recent court case has cast some doubt on the actual limits.
  Check out the Academy of Model Aeronautics for the organized hobbyist's view. http://www.modelaircraft.org/documents.aspx

I have to comment some of these answers. I fly "real" aircraft as well as R/C aircraft.
Flying at thousands of feet of altitude in violation of regulations IS dangerous, whether over an airport or in a desert. VFR airplanes and sailplanes routinely fly only a few thousand feet up, and the operation of RC aircraft at those altitudes is reckless. I personally nearly collided with an RC aircraft during a VFR flight as I approached an airport for landing. At the time I was at approximately 1500' AGL. The R/C plane missed my windshield by less than a wingspan.
Evan an unpowered balsa wood toy aircraft is dangerous. If an aircraft propeller blade hit it, it could damage the prop, causing it to become unbalanced, resulting in damage to the engine. While extreme (and probably very unlikely scenario), it is valid. Just because an object is lightweight or unpowered does not mean it does not present a danger to real world aircraft. Just because you "safely" broke the regs 1000 times doesn't mean it will be safe the 1001st time.
While I agree that many government regulations are overbearing and may overreach their authority, encouraging people to flout regulations is not a good way to build credibility for R/C enthusiasts. It will just end up hurting the sport for all of us.

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text:
Why and how were "eybrow windows" helpful in tight turns?
It is written in some answers that "eybrow windows" were helping pilots in "tight turns". How did this work? These tiny windows seem located right above the head, so I would not expect to see anything else than the sky right above through them, regardless if turning or not.

They would be pretty useful in steep angle of bank turns.  What about that are you not understanding?

In a (steep) turn, airplane is actually flying partially upwards relative to the cockpit directions. It is simply because the turn is (usually) flown with more-or-less constant altitude, but the airplane is significantly banked, so plane of motion intersects cockpit in the same, bank, angle.
So these windows are located approximately in the direction where you are just going. As long as you see only sky there, everything is fine and as it should be. :) But would there be an another airplane, you really want to see it while there is still time to avoid a collision. Whatever you see through front window during a steep turn is either not on your flight path at all or about to collide with nose in nearest following seconds.

Every circle is also partially a looping. +1


text:
What type of engine/motor is used in aircraft APU?
Is the APU a mini-jet engine, or some other type of motor? I know its purpose is to provide power when the engines are off, but what kind of motor/engine is used to generate the power?
I assume this differs from one type of aircraft to the other, but for the purposes of narrowing down the responses - I would like to know specifically about Boeing's APUs lets say on the 737NG.

Since the only fuel available on an airliner is kerosene, the APU is a kerosene-powered jet. Using a different and maybe more efficient type of engine would require an independent fuel system, which does not make sense for the small savings possible.
From the 737.org page on APUs:

There are many different APUs available for the 737. The most common
  is the Garrett GTCP (Gas Turbine Compressor [air] Power unit
  [electrics]) 85-129. This was standard for the series 1/200 but when
  the -300 was introduced it was found that two to three times the
  energy was needed to start the larger CFM56 engines. Garrett produced
  the 85-129[E] which had a stretched compressor, ie the impellers were
  lengthened and the tip diameters increased. When the 737-400 was
  introduced, even more output was required and Garrett produced the
  85-129[H]. This has an Electronic Temperature Control which limits hot
  section temperatures depending upon demand and ambient temperatures.
  By 1989 the 85-129[H] was the most standard APU in all 737 models,
  although there are actually 14 different models of the 85-129 in
  service with 737s.

To answer your question about the 737 NG, it continues:

Other APUs available are the Garrett GTCP 36-280(B) and the
  Sundstrand APS 2000 on the 3/4/500; and the Allied Signal GTCP 131-9B
  for the NGs. The main difference between them is that the Garrett is
  hydro-mechanical whereas Sundstrand and Allied Signal are FADEC
  controlled.

Be sure to load the 737.org page, it has lots of pictures and data on the APUs.

You can modify a diesel engine to run on Jet-A. But I believe that a reciprocating engine would be heavier than the jet.

@ratchetfreak: Yes, and it would need an additional compressor. You get that part almost for free in a jet. The fuel economy would be better, however.

@ratchetfreak "I believe that a reciprocating engine would be heavier than the jet." Based on some of the diesel blocks I've seen, I could imagine one being heavier than a B737-NG!  ;)

@ratchetfreak: You don't need to modify the diesel engine; they run just fine on jet fuel as is.


text:
How can an airplane fly upside down?
I thought the shape of the wing gave an airplane upward lift. How can it fly if it's upside down?

Also relevant: http://xkcd.com/803/ :-)


text:
Why do the stabiliser trim wheels not move exactly in sync?
I've watched a few videos about the Boeing 737, and in particular because it's a bit of a current topic, about the stabiliser wheels in the cockpit.
On some of these videos, which are often in commercial flight simulators, we see the stabiliser wheels rotating backwards and forwards automatically. On the wheels there are white marks. However these white marks are often not synchronised and level with each other, for example this video, or this GIF below from here:

There are other videos where these marks are sometimes nearly 160 degrees out from each other. From my naive expectations, shouldn't these marks be within a a few degrees of each other to accurately represent that the stabilisers are at the same level?
Or, are stabilisers individually independent such that the left stabiliser may need a more acute angle of attack whereas the other may not?

They are in fact moving at the completely same time. It would be catastrophic if they didn't ^^.
The way the white parts are marked on the trim wheels makes us think they move delayed.


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What is a running rabbit?
My father used to work as an air traffic controller, and often I heard mention of a 'running rabbit'.
Obviously, vermin on the runways of airports can be a bad thing, but I don't think he was literally talking about animals.

For what it's worth, I've always heard them referred to as "the rabbits" and never the term "running rabbit".

Likewise - although I've actually only heard the singular 'rabbit' - I understood that the phrase is a reference to the lure (historically, a live rabbit) used in Greyhound racing.

Background
The Sequenced Flashing Lights are part of some approach lighting systems and are a row of strobe lights that flash in sequence to direct the pilots eyes to the runway.  They are useful in conditions of bad weather, as they quickly catch the eye and help the pilot locate the runway threshold which might otherwise be hidden; however, during normal operations they can actually be distracting.  These lights appear to run towards the runway and are often called chasers, the rabbit, or the running rabbit.
Kill the Wabbit
Because these lights are very bright, and often distracting during normal operations in clear weather, it is not uncommon to hear pilots ask the controllers to kill the w/rabbit on their approach.  I personally find them overkill, and have heard many other pilots asked them to be turned off as well.

Photo credit ATG Airports

I sure as hell hope this is never the view I see while on approach!

@MatthewPeters that, indeed, would give whole new meaning to "kill the wabbit"

Ha! Yeah, the 'wabbit' would be very dead after that approach. Probably the aircraft and possibly the pilot, too.

@Matthew Peters:Check out American Airlines Flight 1572 on Wikipedia.

Check out this YouTube video.  Between approximate 0:18 and 0:30, you can see a set of strobe lights leading up to the runway.  They flash in sequence to make a moving dot that runs up the runway.
That is the "rabbit".

I'd like to point out that his approach was too high according to the glide slope indicator

You can also check this video: https://www.youtube.com/watch?v=b-JmZzBl70c

@MichaelKjörling: That video is from a flight sim, and is focused on showing the light system, not demonstrating a good landing.

@DavidWilkins not uncommon for light aircraft to ignore the PAPI and approach more steeply / visually. One instructor told me to ignore it because it guides me way too far into the very long runway (290 meters from the threshold), forcing a longer taxi.

@αCVn: Reminds me of most of my landings (or "landings") in Kerbal Space Program...

"Running Rabbit" is a colloquialism.  It refers to the sequenced flashing lights that lead up to the runway threshold, which are part of the ALS (Approach Lighting System).
From the wikipedia article linked above:

Sequenced flashing lights are sometimes colloquially called the rabbit or the running rabbit.

Running rabbits can also be a reference to primary targets appearing on a radar scope in a sweeping arc, often caused by radar interference from another radar or other spurious RF.

Source?  I've never heard of such a term.


text:
Do airliners have integrated ladders that lead right into the cockpit?
I was watching World War Z and when they were bailing out of Israel, a bunch of armed troops held up a Belarus Ariways Airbus A310 right on the runway.  The pilots dropped a ladder out from near the front of the plane and our heroes climbed up out of danger and directly into the cockpit.  Is this a real thing or just Plot Device™?

Cockpits will have emergency egress methods like ropes or ladders that once deployed can be used for ingress.

@casey often this means punching out a hatch or window plate that would make going for a flight afterwards challenging. Not sure about the A310.

@dvnrrs depends on the plane. Many airplanes have windows that can open and close (e.g. emb-145, b737) or hatches that can be closed again.


text:
If a pilot license is revoked by a country's aviation authority, can the pilot still obtain another license?
There was a recent new story of a Kuwait Airways pilot that got his license revoked after an investigation into an incident on an international flight where unauthorized persons were allowed on to the flight deck.
You can read more about the actual incident here.
Can this pilot still obtain another license to fly commercially?

Related

It depends on the regulations in force. Usually, depending in the reason for revocation, the pilots can apply for recertification after a set period (usually one year) where they have to go through the whole process again. For example, according to 14 CFR 61.13,

(d) Application during suspension or revocation.
...
(2) Unless otherwise authorized by the Administrator, a person whose pilot, flight instructor, or ground instructor certificate has been revoked may not apply for any certificate, rating, or authorization for 1 year after the date of revocation.

It appears that these pilots too, can get another certificate after an year. According to Kuwait Civil Aviation Safety Regulations, Part 1,

1.2.11 Surrender, Suspension or Revocation of License, Certificate or
  Authority
...
3) Unless the order of revocation provides otherwise, a person whose
  License/ authority /certificate is revoked, may not apply for any
  License, certificate or authority before the elapse of one year from
  the date of revocation.

In this document, the term certificate means license?

@BurhanKhalid In case you're  asking about the FAA document, the terms are used interchangeably. The KCASR, on the other hand specifically mentions both though I think it that here too, they are interchangeable.

It depends on the regulations of each specific country but for example in the EASA regulations under FCL.305 CPL – Privileges and conditions:

Conditions. An applicant for the issue of a CPL shall have fulfilled
the requirements for the class or type rating of the aircraft used in
the skill test.

More research would be needed to answer your question (i.e. to see if there are other regulations that may prohibit somebody from obtaining a licence as you described in the question) but under this paragraph no such prohibition (condition) is mentioned; it would probably be best to contact the authority and ask.


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When aircraft is flown by the pilot and when by the autopilot? What are common procedures?
I am courious about different phases of flight in which airplane is flown by the Pilot, and when by the Autopilot.
For example, I'm quite sure that generally pilots have full control during takeoff and landing (full control? stick and throttle?) but during cruise at high altitude is the autopilot that has control.
But when a pilot activates autopilot? immediately after takeoff? And when take control again?

What is your definition of autopilot? For example during take off and most of landing, autothrottle is used...

It depends a lot on the aircraft type, as well as the pilot, weather conditions, length and type of flight, etc.  This is a pretty broad question; like asking how often people use cruise control in their cars...

@RonBeyer The autothrottle is considered to be a separate system than the autopilot. They're both part of "the automation" and the FMCS and a few other things, but at least in the 737 world, the two terms are distinct and do not overlap.

I understand the overlap and distinction, but the OP may be lumping all computer flying under the broad "autopilot" term, which is why I asked if they want to specifically know "autopilot" or in more general computer control terms...


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Why developing F-35 is harder than F-22?
I'm sorry if I'll be not so accurate in my description but, please, try to understand "core" of my question.
F-22, ignoring high cost of each aircraft, appear to be a successful project, developed and delivered in almost desired timeranges respecting requirements.
I sincerely don't understand why F-35, that initially was thought to have almost same stealth performances of F-22 but at an individual cheaper cost, is running into troubles, difficulties, risk of abandoment since years.
Develop is still ongoing and reliability and performances are still not satisfied. I thought that experience based on first stealth high perfromance fighter jet could help and speed up an aircraft like f-35 that should have lighter requirements but facts are demonstrating the opposite

They just wanted the stealth of the F-22 and the V/STOL of the AV-8 in one aircraft for a lower price, with carrier variants as well, which also needs to replace the A-10, F-18, and F-16.

Developing a plane that's good at everything is quite a bit more complex than developing a plane that's good at a couple of things. Oh, wait, that's what @fooot said... ;)

Also, the F-35 is project with 9 countries and about 20 companies involved, which makes it a political nightmare. Each country has a set of requirements from their respective military bodies (navy, air force, etc) and wants local companies to have the biggest share of the investments.

Because they wanna combine 3 aircrafts into one plane


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How a customer could choose "A330-Neo" or "A350 Regional" on shorter routes?
According to Wikipedia, Airbus is studying a new A350 Regional that effectively is a think that I suggested some time ago when I asked "Why is the A330neo more efficient than the A350 on shorter routes".
In that question I said:

why for shorter routes A330neo is more efficient than A350? Could not
  be enough to have an 350 with lower fuel capacity (in case shorter
  length) and maybe reduced engine power (the opposite of higher power
  in A350-1000) thanks to reduced weight?

Now, it seems that with this model Airbus is creating a more evident overlap in its proposal to market for shorter routes because, as written in A330neo Wikipedia page, is written:

A330neo enables profitability on shorter ranges where the longer-range A350 and Boeing 787 aren't optimized.

So what reasons could push a customer to choose to A330-Neo or A350 Regional on shorter routes?

This probably just boils down to the economics of the route. An aircraft for a route is chosen based on more factors than just fuel efficiency. Airlines have to weigh in other factors like:

Number of landing/take-off slots available at the airport

This is because an airport can only support so much traffic. It may be more economic to fly a larger aircraft with more seats than multiple flights.

Cost of gates/landing fees, etc

Airports make money by charging per-passenger and per-aircraft fees. If an aircraft is parked at a gate, it is costing the operator to be there, so the more aircraft the more expensive it gets. Airports may charge depending on the size of the aircraft as well.

If the airport is equipped to handle an aircraft of that size. Some regional airports can't handle larger aircraft (either from a gate/facility perspective or a runway/taxiway surface one).
How many passengers need to travel that route on a daily/weekly basis
Regional fuel costs
Training/currency requirements for pilots and how easy it is to move between them

If going from the A320 to the A330 is a simple course vs the A350 being a whole new endorsement, they may choose the A330 to be able to have higher utilization of the existing pilots vs having specialized crew.

Same as above except substitute mechanics, spare parts, etc. This is a major reason that Southwest only fly's 737's, short or long-haul.
Ability for the aircraft to service other routes.

All said and done they need to pick the aircraft that is the most economic for the intended mission and fits into the business model of the company more. Airbus isn't going to take a customer that wants the A330 and push them into an A350, it isn't like buying a car where the salesman upsells you, the customer by the time they approach Airbus for a purchase contract already knows exactly what they need. Think of it more like buying tools (where you need exactly the right tool for the job) than it is about buying a car (the Corvette is nice, but have you looked at the Prius?)...

A330 and A350 have a common type rating: https://www.airbus.com/newsroom/news/en/2014/10/the-common-type-rating-is-approved-for-a350-xwb-and-a330-pilot-training.html


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Why B-52 was not re-engined as a more efficient 4-engine?
Why B-52 was not re-engined as a more efficient (also for maintenance) 4-engine but is still an 8-engine aircraft?
In history, almost all others models were re-engined with new engines also quite different from original, some examples could be C5 Galaxy or also B737 that in latest geneations requires also to extend undercarriage or make bottom "flat" area of engines, to accomodate new bigger ones.
So why B-52 remains the original projects despite its long history? Did development cost be affordable in this very long period?

I looked for that but strangely I did not find it with embedded search engine... thank you

https://www.defensenews.com/video/2019/06/20/heres-how-the-air-force-wants-to-re-engine-b-52-bombers/

There were several proposals to do just that, none of them ever went beyond the proposal phase.
Part of the reason is almost certainly the large stockpile of spare engines the USAF had (and maybe still has), taken in part from re-engined KC-135s.
Part of the reason no doubt is also that there have been near constant plans to retire the B-52 "soon" and a major project like this was never deemed economical.

B-52's are going to remain flying through 2050, so "soon" isn't very soon.

+1. Another way to describe the aspect of being retired “soon”, is that the B-52s don’t do a lot of flying hours per year, especially when compared to passenger aircraft. So, the cost/benefit analysis isn’t very favourable, because you have the same cost to replace no matter how much you fly, but the benefit only occurs if you fly a lot before the aircraft is retired.

@RonBeyer that's the latest plan. Back when reengening was considered it was thought the B-1 was going to replace the B-52 within the decade. Later it was thought the B-2 was going to replace the B-52 within the decade. Neither happened of course, the B-1 is gone and the B-2 looks to be the next to be replaced while the B-52 keeps soldiering on.


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Why is the A330neo more efficient than the A350 on shorter routes?
For A330neo Wikipedia page, is written:

A330neo enables profitability on shorter ranges where the longer-range A350 and Boeing 787 aren't optimized.

For what reasons it is true?
A330 and A350 have almost the same size, weight and passenger capacity (the undeveloped A350-800 should be also more similar), and also engines are very similar, the same family Trent 7000 vs Trent XWB.
I thought that with almost similar planes, the bigger difference for calculating range could be only the fuel capacity (surely bigger for A350), but efficiency (in terms of lower weight due to advanced materials, lower fuel burnt due to new engines technologies) could be an "always true" concept.
So, why for shorter routes A330neo is more efficient than A350? Could not be enough to have an 350 with lower fuel capacity (in case shorter length) and maybe reduced engine power (the opposite of higher power in A350-1000) thanks to reduced weight?
I found this similar question, but I think that mine is more focused to general concepts because I'm asking also "what makes an aircraft more optimized for longer/shorter routes.

I don't think fuel capacity is an issue in determining which one is more efficient for a very simple reason: airlines almost never fill tanks to full capacity unless there's a good reason to do so, e.g. regulation calls for it due to the distance to be flown, fuel is cheaper at the current station than at others, and the savings outweigh the cost of carrying the extra fuel to the next segment, etc.

@JuanJimenez Fuel capacity does have an impact on weight. For example, the standard A333 has no center tank, so they save weight on sealing, plumbing, pumps, and the interting system. Some other long range aircraft involve the installation of cargo bay tanks and activation of the trim tank. There's follow-on effects for designing for the mass of the extra fuel, in particular with landing gears (see A330 vs A340), bigger engines and a fuel dump system.

@user71659 Problem with that argument is that the A350 can carry more passengers, so in the end the additional hardware is a wash.


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Why didn't the A330neo and A320neo share the cockpit of the A350?
Recently Airbus presented its lastest projects A330neo and A320neo.
I'm sincerely surprised about the cockpit, in that it is essentially the same of the original A330, while I was expecting that renovation would affect not only the engines, installations, and lights but also the cockpit instrumentation taking inspiration from the new bigger screens of the A350.
I know that in this way the training for pilots is much easier, but at the same time I think that if a new cockpit is developed for a new plane (taking into consideration that "Type Rating" is anyway considered the same), it should be because of more safety, readability, and situational awareness.
In the past Boeing completely updated its cockpit inside the B747-400 and B737NG models from the original mechanical/analog gauges to the new glass cockpit. In those cases, surely the necessary training was very hard for pilots so, why not now for minor updates?

you're comparing apples to oranges when comparing Airbus and Boeing approaches, they are two different companies and what one does does not mean the other thinks is the best - 2. "it should be because of more safety, readability, and situation awareness" [citation needed]

It's beacuse I don't understand different approach that maybe someone could explain something about this topic, like in other questions was explained different approach between joystick and yoke of different manufacturers.
I suppose that these could be reasonable "reasons" for update, if you have other indications, please provide them :-)

Because then you have to retrain and requalify all of the existing A320/A330 pilots, as well as getting rid of all your maintenance expertise and spare parts, becomes expensive. The 747 was a little different because they also got rid of the flight engineer.

(ma che t'hanno fatto di male gli articoli determinativi?) anyway 1) ok, fair point. be aware though that the answer is not necessarily "logical" (i.e., marketing might be involved) 2) my "citation needed" referred to the given reasons, i.e. I would like you to show that those benefits actually are there, before asking why they have been neglected.

@RonBeyer That looks like an answer. (I guess you didn't post it as one because you don't know that it's the reason; but you could always phrase it as "A significant disadvantage of doing it that way would be...")

@DavidRicherby I was in the process of typing it up when Gerry answered pretty much what I did, so I'll leave it with his.

The short answer is that it's what the market wanted.  There is  always a lot of discussions between the airlines and manufacturer's before Airbus or Boeing commits to building a new aircraft.  In this case both Boeing and Airbus came to the same decision -- the airlines were being driven by one single factor to replace their A320 or B737 fleets, they just wanted to reduce fuel expenses.  That's why the Airbus is the 'neo' new engine option.
The airlines made it clear that any new aircraft purchases would be based on operational savings and that's primarily driven by fuel burn and the resulting costs.  The solution to that is a new engine.  Putting in a new flight deck is a huge expense for the manufacturers which would drive costs up and the airlines won't pay extra for something that doesn't save them money.
There's no cost benefit to a new flight deck, especially when (as others noted) you have a huge investment in an existing fleet.  In fact, all it's likely to do is add costs.  With a new flight deck you'll have a huge increase in maintenance and spares costs due to the need for stocking more parts with new part numbers (just adding a part number to a logistics system costs significant money.)  You'll also need new crew training simulators due to the different displays and controls, whereas the neo option can be handled with software upgrades.  And if it drives a need for new type ratings, that would mean more training costs and making sure you have the crews with the right rating at the right time.
In my experience in 20 years dealing with this market, airlines only spend money for two reasons:

It will increase their profit margins
The FAA (or other regulatory agency) mandates that they have it.

Aside from that, you should consider Airbus' side.  They're trying to sell airplanes and they have to compete with Boeing.  Since the avionics architecture is quite different between the A320/A330 and the A350, moving to it would add huge costs and a couple years delay in entry into service.  They also have to deal with the fact that airlines don't want to see a big price increase.  Prices for the A320neo and B737MAX are not significantly higher than the current/older versions.  If the competition can offer a 7 to 9% reduction in fuel burn for approximately current prices, spending an extra 2 or 3 years to match that with a new flight deck means a lot of lost sales in the interim.  And you probably won't make enough margin to recoup the new flight deck costs.

Great answer. You may want to put in something about the added costs of training pilots & maintenance on a new flight deck plus the cost of spares already in stock that are no longer usable, in addition to the manufacturer cost of refitting the A350 flight deck into the A320/330 cockpit.

@FreeMan  Good point, but I have to deal with it in spare moments between real work.

To add to Gerry's answer (and this will be slightly too long for a comment), there is a huge disadvantage to drastically changing the cockpit when going from an A320 to the A320 NEO or from a B737-300 to the B737-700, or 737 NG to 737 Max, and that has to do with the existing fleets.
If you keep the cockpit basically the same and just add what new switches are needed for the new engines, then most if not all operators can qualify their pilots in both models, and integrate the new arrivals into the fleet with minimal disruption.  Need to substitute a NEO for a standard 320? No big deal, the same crew can fly either one.  If the cockpits are wildly different, then the new jet is essentially a different type rating, and the pilots will have to be qualified (Edit: "qualified" in the airline sense -- current & qualified, not just type-rated) in one or the other, but not both at the same time.  So when you substitute an aircraft, you have to change out the crew as well.  That adds up to a lot of overhead, training costs, and scheduling inefficiencies.
In the case of the A-350, it IS a whole new aircraft, and nobody would be qualified in it at the same time as the A-330 or A-320, so there's no great need for backward compatibility.  But in the case of the A-320 NEO, keeping commonality with the existing A-320 fleet so that pilots aren't restricted to one or the other is a big deal.
Now, I can just hear the objections... you said "B737-300 to B737-700 -- that's steam gauges to glass!"  Yeah, sort of.  BUT: Boeing "dumbed down" the 737 NG cockpit tremendously compared to what it could have been so that operators of the 737 classics could keep their pilots qualified on both the classic and the NG simultaneously.  There was the "6-pack under glass" option for the NG displays, which made the NG display look like round dials, so that pilots used to the Classics had reasonably similar displays when they flew the NG.  Less noticeable but still important, the overhead panel and the automation of the NG's was kept essentially the same as the classics, even though advances in automation would have enabled a FAR more modern approach to nearly every system in the aircraft and their management.

The option to digitally display round dials -- source page.
Another image -- showing how even the engine instruments were not much more than digital depictions of the round dials:

Original link.
Consider: the 737 NG is a more recent design than the 777, but the 777 aircraft in 1996 had automation light years beyond what even the 737 Max rolling out this year has.  The overhead in the Max looks essentially identical to the overhead in the NG, very very close to the overhead in the Classic, and not dramatically different from the overhead panel of the 737-200 from the late 1960's!  Why? So that airlines never had to segment their crews.
If the 737 Max were being rolled out "in a vacuum" today, its cockpit would look a lot more like the 787's -- which was mostly a "clean sheet" design (some commonality with the 777 flight deck).  As was the A-350 -- clean sheet of paper.  But the B-737 Max and the A-320 NEO aren't "clean sheet" designs and keep significant commonality with their predecessors, because that's what the airlines insist on.
For better or for worse.

I agree with the answer but you have an implication that an A320CE can't also be qualified on an A320NEO, which isn't true. Same for having a pilot qualified on the A350 that could not also be qualified on the A320/330, which also isn't accurate. Adding a new type rating doesn't remove the old one...

Not trying to imply that the same pilot couldn't be qualified on all versions of the A320 at all -- quite the reverse! As to the 320/330/350, the type ratings would all still be there, but in practice airlines don't tend to keep pilots current on multiple types, so an individual would, at any one time, be either "an A320 pilot" or "an A350 pilot", but not both. Of course, having been thru the course in the past, training would be quicker to go back into it & there'd be no need for a type-rating checkride. But "current+qualified" on multiple types at once is rare-to-never for most airlines.

"...and the pilots will have to be qualified in one or the other, but not both at the same time" Maybe change the word "qualified" to "current"? Probably the same with "A-350, it IS a whole new aircraft, and nobody would be qualified in it at the same time as the A-330 or A-320,", it just sounds like you are saying that a pilot cannot be qualified in both, which is possible (and probable for an A320->A350 transition), but most likely wouldn't be current in both.

Edited to incorporate that.  For an airline, if you aren't current in whatever, then today you aren't qualified to fly it for them.  A pilot who flew the 737 two years ago but is now flying the 777 may be "qualified" to fly the 737 in the FAA eyes for Part 91, but for his airline, no, he isn't, and they wouldn't put him in that airplane to fly it under any circumstances.  As I mentioned, the requal training would be shorter than an initial course if he went back to the 737, but it would absolutely be re-QUALIFICATION in the aircraft as far as the airline was concerned.

@RalphJ Airbus has a scheme out that is EASA and FAA backed called Cross Crew Qualification, and applies to all Airbus FBW aircraft, allowing crews to be type rated on multiple Airbus types with highly reduced currency requirements.  Many airlines take advantage of this.

The short answer is money.  The B747-400 and B737-NG are indeed very different airplanes from their predecessors.   So much so that they were deemed different type ratings.  Getting a new type rating for pilots at an airline is a much more rigorous task, and expensive.  Consider the administration overhead, to add the necessary Ops.  SPECS, Aircraft Operations Manuals, etc. and have these all approved by the FAA or equivalent, and add in mechanic retraining and certification and you've got a huge investment.
The NEO engines and the planes themselves are a little different operationally.  I fly them at work sometimes.  But their not so different as to require a new type rating.  The differences training we went through was a basic slide show, memorizing some new numbers, a handout of differences and a pretty basic test.  All standard for differences training.  No special or sim training was required.  Even the mechanics just have written material to read through for the new engines.  Huge cost difference.  Bottom line, the airlines get the huge fuel savings and no required costs for retraining folks.


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Winglets vs Sharklets vs Blended wingtips
I tried to look for this answer but I was unable to find a complete one.
What is the differences between Winglets, Sharklets (used for example on A350 XWB), and "Blended wingtips" (used only on 787)?
Especially firt two seems very similar. Anyway, more in general, what are differences/PROs/CONs of these different solutions?

The difference? Marketing!

@PeterKämpf marketing? weren't you the one that kept repeating that the raked wingtip from 787 solution is superior to the winglets?

closely related: Is wingtip design mature?

@Federico: If raked wingtips had been on the list, my answer would had been different. But they weren't.

@PeterKämpf is there a 787 variant with any other wingtip type?

@Federico: Right, missed that. The 787 has only the raked sort, precisely because they are better than any of the other. So my comment refers only to the listed types, not the one inferred by mentioning the 787.

Winglet advantages

With a winglet you see a 3-5% reduction in drag which helps increase efficiency in aircraft by reducing something called a wing tip vortex which forms by the high pressure(under the wing) wraps around the top part of the wing which has the low pressure and results in a wing tip vortex. A winglet works by deflecting the air so less high pressure wraps the wing tip.
Increases lift(the winglet generates lift also like an aircraft wing)

Winglet disadvantages

Adds about 300 lbs of weight to the aircraft depending on the winglet
Reduces maneuverability which is why you don't see a winglet on a fighter jet

Now a sharklet and a winglet are essentially the same thing.
Bts: Its called a raked wing tip
Raked wing tip advantages

Does the same thing as a winglet by deflecting the air. With a raked wing tip you actually see a greater drag reduction than a winglet can give you which leads to great efficiency in aircraft

Raked wing tip advantages

You actually loose a little bit of lift due to the raked wing

Sharklet- The sharklet deflects air just like a winglet and acts in the same way and is a winglet, but Airbus just named it differently.
A350 design- The a350 uses a sharklet and a raked wing. You see great numbers of efficiency in the design because you include a raked wing and a sharklet.
Between the 3 you mentioned there is a big difference and all 3 have different advantages and disadvantages. They all act in the same way by deflecting the air the design is just different for each one. I hope this helped you understand a little bit more about these devices.

I provided a wiki link twice in the answer to help you learn more about the difference between the 3 devices.

Please not too much negativity on my answer. I honestly do put a lot of thought ,effort, and lots of my time to answer questions. I was almost late to school this morning because I put 40 minutes of my time into my answer.


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Why scrap an A380 with only almost 10 years?
Accordingly to this article "First commercial Airbus A380 turned to dust", first A380 was scrapped.
Apart be a sad news for an aviation fan, it sounds me a bit strange because it was an airplane of only 10-12 years, while generally a plane flights for more than 20.
Ok, I know that A380 was sadly almost a commercial flop but it was not an old plane, I thought that could continue to flight with another airline.
In which way could be more convenient to scrap it instead of sell it flyable to another company?

Although the question maybe isnt a duplicate I think this answers your question too: https://aviation.stackexchange.com/a/72001/100

If nobody wants to buy it because it's too expensive to operate/maintain, what would you do with it? Mothball it and continue to pay, or scrap it and recover some of your investment?

One need to take into the equation, that this particular frame was MSN003, so one of those affected by the wiring disaster and other teething troubles of the early manufactured models, which substantially increases maintenance costs. Dr. Peters Group says "we did not find a buyer" and this might be the root cause. The plane has larger value as spare part source than complete. I remember some Frontier Airlines A318's which were sent for part-out after only two years of service, so it is nothing unusual in this business.

Well, the article you are referring to quite clearly states the reason for the decision to scrap the plane(s): negotiations with airlines to sell or lease were not successfull, so the only option was to scrap, or rather dismantle the plane.
Furthermore, the article presents the estimate by Dr. Peters Group that it would be able to generate some \$45 million  per aircraft by selling the useable components, and an additional  $480 000 / month by leasing the engines.
As a reference, the list price of a new A380 is (was) something like $ 430 million, the actual prices being, however, much lower. When you consider that a 10 year old plane most likely needs a considerable interior refurbishment, the decision made by Dr. Peters Group does not seem so strange, does it?


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What is the force exerted by the catapult on aircraft carriers?
On aircraft carriers there is a catapult that slingshots aircraft so that they can gain lift on the short carrier deck.
I have a few related questions - the first is what is the force exerted / required by the catapult to sufficiently accelerate the aircraft; and is it adjusted per aircraft type or a uniform value?
I imagine carrier takeoffs/landing cause additional stress on the aircraft; but does it have a dramatic effect on the lifetime of the aircraft vs. their non-carrier configured twins? Or is it compensated for by a more frequent maintenance schedule?

I do know that they have to adjust the force for each plane as it moves to the head of the queue, but I haven't the foggiest how much it is beyond a lot ™.

It is absolutely adjusted for each type of aircraft, just like the arresting gear. The other part of your question about how much force depends on the weight of the aircraft and the speed required at the end of the launch. F=ma after that.

Total force or impulse force?

@SMSvonderTann, force is force. Impulse is something else (force times time, equal to change in momentum).

From Can carrier-based aircraft takeoff while the carrier is stationary? conventional: 95 MJ, EMALS: 122 MJ. Also China building two aircraft carriers (EMALS): 120 to 140 MJ to launch an aircraft.

The force applied by the steam catapult is adjusted according to the aircraft T/O weight (by extension, the type). The catapult has to accelerate the aicraft to some airspeed at the end of the launch procedure. This required force depends on the aircraft mass. From USN T-45 Flight training instruction:

Aircrew should pay particular attention to the A-sheet’s basic weight, fuel and store loads to ensure the gross weight calculation is correct. This is particularly important when launching from the boat because the catapult needs to be set correctly.... Taxiing up to the catapult, a green shirt will hold up the weight board. If the weight on the board matches the weight on the weight chit, acknowledge ...

In case of steam catapults, the force, once set, is fixed; one advantage given for the Electromagnetic Aircraft Launch System (EMALS) is that the force could be adjusted by the system to keep the speed near the requirement. From airspacemag:

The amount of steam needed to launch an airplane depends on the craft’s weight, and once a launch has begun, adjustments cannot be made:... The launch control system for electromagnetic catapults, on the other hand, will know what speed an aircraft should have at any point during the launch sequence, and can make adjustments during the process to ensure that an aircraft will be within 3 mph of the desired takeoff speed.

Carrier launches and recovery is one of the most stressful things the aircraft can undergo; however, the aircraft are designed to handle these, for example, via a strengthened landing gear and fuselage. Due to these, carrier aircraft have lifetimes comparable to that of land based aircraft.
Carrier (in general, naval) environment is hostile to aircraft and as such, the maintenance schedule is different (and more extensive, for example checks for corrosion) in case of aircraft.

So essentially EMALS can fix incorrect weight setting.

Huh... I thought the only large boats in the U.S. Navy were submarines.  I didn't realize they referred to aircraft carriers as boats.

I was in the Navy. Technically, vessels over a certain size are "ships", and under that size are "boats". But in conversation, they're all "boats"... "I'm drunk, ready to head back to the boat?"

@JanHudec, not necessarily. A heavier aircraft needs more speed to get airborne. If the wrong weight value is entered in the computer, the launch will happen at the speed calculated for that weight, which might not be enough speed for the actual weight. Unless it can calculate the acceleration expected based on power input and realize that it's not accelerating fast enough, then increase the power until it is.

@FreeMan, for different types, weight and take-off speed are only loosely related as wing loading is what determines the speed. But as long as it has the correct type, it could adjust the speed for the sensed weight, or simply always launch at the speed corresponding to MTOW. Or maybe it could go the other way and abort the launch if it senses the weight too different from what was set—something is wrong, so stop while possible and let the crew fix the problem whatever it is.

@Steve the demarcation between ship and boat used to be 77 feet.  A Marine I know said it better: a ship can carry a boat, but a boat can't  carry a ship

Takeoff
Steam/power settings are adjusted for each a/c type and T/O weight.
The EMALS stores 484 MJ in four 121 MJ alternators spinning at 6400 rpm. It delivers up to 122 MJ over 91 m. That averages out to 300,000 lbf. EMALS more finely controls launch forces (Max Peak-to-Mean Tow Force Ratio = 1.05), allowing it to launch smaller a/c (eg, smaller UAVs) and delivering a smoother ride that reduces airframe fatigue.
Current steam catapults deliver up to 95 MJ over 94 m. Each shot consumes up to 614 kg of steam piped from the reactor (NB: not the primary coolant loop). That averages out to 230,000 lbf.
Accelerations average around 3 g's, peak around 4 g's.
Landing
Landings are stressful (notice the fuselage skin wrinkling beneath the radome on this Hawkeye):

(Source: DoD photo by: PHAN KRISTOPHER WILSON, USN Date Shot: 11 Jan 2005.)
An F/A-18 touches down around 720 fpm (12 ft/s). It's rated to twice that. CTOL fighters typically do about half that. I believe airliners average under 200 fpm (3 ft/s).
Here an F/A-18 is dropped from 20ft (36 ft/s, 2200 fpm):

Service life
NATO fighters are typically designed for 30 year service lives (6,000 to 8,000 flight hours). Historically, Soviet/Russian fighters fly much less. The Su-27SK is rated for 2,000 flight hours over 20 years. [See table for cost and service life comparison.] F/A-18's were built for 20 year service lives, 30 years with service life extensions.
The fuselage and landing gear are much stronger to withstand carrier landings and launches. The nose gear regularly transfers 4x the takeoff weight of the a/c into the rest of the fuselage.
Compare the F-35A's CTOL nose gear:

(Source: USAF)
...to the F-35C's CATOBAR nose gear:

(Source: USN)

Here's an excerpt from a Naval Air Warfare Center paper on EMALS:

Other drawbacks to the steam catapult include a high volume of 1133 m3
  , and a weight of 486 metric tons. Most of this is top-side weight
  that adversely impacts the ship's stability and righting moment. The
  large volume allocated to the steam catapult occupies "prime" real
  estate on the carrier. The steam catapults are also highly maintenance
  intensive, inefficient (4-6%), and their availability is low. Another
  major disadvantage is the present operational energy limit of the
  steam catapult, approximately 95 MJ. The need for higher payload
  energies will push the steam catapult to be a bigger, bulkier, and
  more complex system.
Endspeed:      28-103 m/s [54-200 knots]
Cycle time:    45 seconds
Weight       < 225,000 kg
Volume       < 425 m 3

At max speed, the output of one of the disk alternators would be 81.6
  MW into a matched load... These magnets have a residual induction of
  1.05 T at 40 oC and create an average working air gap flux density of 0.976 T, with tooth flux densities approaching 1.7 T... Maximum output voltage is 1700 V (L-L) peak and current is 6400 A peak per phase. The
  disk alternator's overall efficiency is 89.3%, with total losses of
  127 KW per alternator. This heat transfers out of the disk alternator
  through a cold plate on the outside of each stator. The coolant is a
  WEG mixture with a flow rate of 151 liters/minute. The average
  temperature of the copper is 84oC, while the back iron temperature is
  61oC.

Sources:

EMALS/ AAG: Electro-Magnetic Launch & Recovery for Carriers
Electromagnetic Aircraft Launch System - EMALS
Steam catapult types
Electromagnetic Aircraft Launch System - EMALS - NAWC

Catapults powered by steam from the carrier's engines, the amount of pressure is set per aircraft according to its weight and how fast it needs to be at the end of the deck. If too little steam power is set the airplane will not get up to speed and will end up in the ocean, too much and the airplane can be damaged by the excess force.
Carrier aircraft have to be much tougher than their non-carrier cousins, and have to be specially designed for those kinds of operations. The whole structure has to be strong enough for repeated carrier landings and takeoffs, and also it has to be able to fit on the elevator, so have folding wings of some sort. They are generally so well built that they last as long as their non-carrier counterparts.

Newer carrier aircrafts use catapults powered by electro-magnets. However, I don't know if they are already in use or still getting developed and tested.

The F-35 is a good example: a family of three airplanes built around a common core design. Why three airplanes instead of two (normal take-off / vertical take-off)? Because the naval version not only needs an arresting hook but also a strengthened fuselage precisely because of the catapult and arresting stresses.

@jklingler: the USS Gerald R. Ford, the first of the newest class of US aircraft carriers will be the first aircraft carrier to use the Electromagnetic Aircraft Launch System (EMALS) which generates 484MJ within 2–3 seconds, enough to accelerate a 45000kg aircraft to 130kt in just 91m.

@JörgWMittag Do you know how many MJ the steam powered catapult generates?

@jklingler: I guess the most powerful one would be USS George H.W. Bush's, but the article doesn't list any numbers. The best I could find was 80,000 pounds (36,000 kg) @ 140 knots over 94m.

The electromagnetic catapults are apparently better for the airplanes as the force is consistently applied throughout the takeoff run, steam catapults give more of their force at the beginning, so more stress.


text:
What is the coordinate system used in an Aircraft?
I know that from nose to tail the aircraft is divided by STA (station). At least for Boeing and Airbus this is the case but I am not familiar with other manufacturers.  However, there is also two other dimensions that give every location of an aircraft an identifiable point location. It's obviously not x,y,z.  What is this coordinate system and approximately what does one unit along each access mean in terms of inches or centimeters?

Stations (STA), generally Fuselage Stations (FS), designate location along the length of the aircraft, increasing from nose to tail. Generally station 0 is somewhere in front of the airplane. One reason for this is that if the airplane grows longer, there still won't be any negative stations, and sections of the plane keep their station numbers. FS 100 can also be placed at an important location (looks like the firewall below).
Water lines (WL) designate location in the height of the aircraft, from ground up. You can probably guess by now that these are holdovers from the marine industry. Like the stations, water line 0 is generally a bit below the aircraft, possibly to have WL 100 at the center of the fuselage, or WL 0 could be at the bottom of the fuselage.
Butt lines (BL) designate location left/right on the aircraft, generally centered in the middle.
While the main system is based on the whole airplane, different parts (like the wings) have their own system of STA, WL, and BL.
The stations are generally in whatever unit is being used for the aircraft. In the US, this is inches.
See this link for an example and further explanation.
For a picture similar to the one below but with more detail, see here.

Swept wing aircraft also use Wing Stations (WS), a reference parallel to the sweep of the leading edge or perpendicular to the wing ribs in the swept portion of the wing.

There is a fair amount of variability between aircraft manufacturers as to how they reference physical locations on their airplanes, especially along the longitudinal axis. Even within a company, different schemes are sometimes used for different models.
For example, on the Boeing 747-100, -200, -300, and -400 aircraft, the reference datum is 90 inches in front of the airplane's nose. Why 90? Because the tip of the 90 inch test probe for pitot tube calibration on the original aircraft was the zero point.
However, for the 767-300 the reference datum is 28.5 inches aft of the airplane nose, which of course means that weight and balance calculations have to deal with negative arms.
Boeing uses two systems to refer to a longitudinal axis location. The Boeing Weight and Balance Control and Loading Manual puts it like this:

Balance Arm (B.A.) A true measure of distance from foward to aft, in inches, from a fixed
  datum. The fixed datum is selected by the airplane manufacturer.
  Balance Arms are used in weight and balance calculations.
Body Station (B.S.) A manufacturing location on the airplane. For first of an airplane
  model, B.S. are continuous from the front to the aft of the airplane.
  For later versions that are either stretched (i.e. fuselage inserts
  added) or shrunk (i.e. fuselage sections removed), B.S. becomes
  discontinuous, for manufacturing reasons.

Another system for referencing a point along the longitudinal axis is the percent of the mean aerodynamic chord (%MAC), and to the best of my knowledge this is standardized. C.G. limits for the various operating envelopes (zero fuel weight, taxi, takeoff, landing and others) use the %MAC for the x-axis and weight for the y-axis. Thus, weight and balance calculations come up with the actual C.G. in, say, inches, and then translate this to %MAC for to see if the C.G. lies within the the operating envelopes. The calculation is straightforward. Take the C.G. in inches, subtract the leading edge of the MAC, divide by the length of the MAC, and multiply by 100.
Note that for purposes of C.G. calculation, the wings have to use the same reference system as the fuselage (or have it translatable in reference to the fuselage) because the C.G. of fuel tanks varies depending on how much fuel there is.
Typically wide-body cargo aircraft have lateral imbalance limitations, and for that the lateral referencing system is used. For the 747-400, for example, the maximum lateral imbalance is 10,000,000 inch-pounds up to 846,000 lbs. From there it slopes to 3,340,000 inch-lbs at 913,000 lbs.

good info. thanks.

I'll piggy-back here.  Usually the station origin is in front of the nose and the waterline origin is below the aircraft.  That way, all arms used for CG calculations are positive -- and you generally only ever deal with positive numbers.  You place the datum in front of the nose (instead of on the nose) because things change throughout the design process and you might need to extend the nose.  One of the other answers mentions an aircraft whose datum makes some of the aircraft negative -- that is likely a derivative aircraft, or one whose nose design changed in the design process.

It is much different with depending on what you are doing. Engineering drawings reference a 3 point system for installations mainly Station (X or FS), Butt Line (Y or BL), and Water Line (Z or WL) these 3 coordinates dictate where things are installed exactly.  If you were to look at the production drawings of those light piston and corporate aircraft you would see these much like the illustrations given by Fooot above.
As you are maintenance, simplified drawings are issued to expedite work. It's much easier to tell you it is Fwd of INBD flap rail than FS XXX, LBL YYY, WL ZZZ, as a technician would be more familiar with the location of the INBD Flap rail than its coordinate location.
If you were building that plane, the coordinate locations would be given as it would have to put in an specified location to comply with the type certificate of that aircraft at least in America.

To my knowledge there isn't a coordinate system to describe locations on an aircraft airframe.  Measurements along the longitudinal axis of the aircraft exist for center of gravity measurements.  These measurements are made as an "arm" measurement from a standard arbitrary point, known as the datum.  Specific measurement locations are "stations".  There is no real need as far as I know to have a measurements in the other 2 axis.
For locating components for maintenance purposes, my experience of technical manuals usually describe locations verbally, such as "the flap actuator can be located forward of the inboard flap rail".
My experience is mainly with light piston aircraft and corporate jets, it could be different with larger aircraft.


text:
Who pays for Air Traffic Control services?
I imagine certain fees from flight boarding sales are paid to the FAA, but who is responsible for paying fees for passenger flights?

What do you mean "fees for passenger flights"?

Typically there are landing fees for large aircraft at airports. There is no standard amount or standard way of calculating them (or at least there wasn't back in the 1990s). Airports had widely varying fee schedules. Whether there was (or is) a differentiation in fees for pax or cargo I do not know. As I remember the landing fee for a 747 at KJFK back in 1999 when I retired was over $12,000. The fees went to the airport, not to the FAA. It might be interesting to post a question to see what the landing fees are at major airports these days.

@Terry Thank you for a great explanation. I was wondering what that has to do with ATC though, as per question title.

@digitgopher I was attempting, perhaps poorly, to respond to the question in your comment as well as to add a little more info as to where money goes. You are right that it has nothing to do with ATC, but as often happens with questions, the question text is more expansive than the title. My comment indeed did not address the title at all, which is why I put it in as a comment rather than an answer. However, it did address, however poorly, what I felt the questioner might have meant to include in "fees for passenger flights."

FAA Funding is currently a mix of General Fund(taxes everyone pays) and Airway Trust Fund(ticket taxes and fuel taxes) money. The breakdowns are shown in: https://www.faa.gov/about/office_org/headquarters_offices/apl/aatf/media/AATF_Fact_Sheet.pdf


text:
Do other countries aside from Israel have some special requirements on wearing seatbelt upon approaching destination but before the aircraft descent?
I read  (mirror) that Israel has enhanced security procedures resulting in airplane  passengers having to wear seatbelt up to 180 nautical miles before the destination:

ISRAEL - TEL AVIV FIR
— Enhanced security procedures
• From before reaching the identification point (see below) until after landing: Switch on the ’Fasten Seatbelts’ sign and do not open the cockpit door except for safety reasons.

The identification point (map) can be up to 180 nautical miles before the destination:

• Overflying flights from Amman: The above procedure applies from TKOF until exiting the FIR.
— MIL identification by Tel Aviv CTL
• E-bound: Before 180 NM from Ben Gurion 'BGN', call Tel Aviv Identification 124.300 (sec. 132.050).
• From Amman: Before 10 NM east of TALMI or SALAM, call Tel Aviv CTL 121.400 or 132.050.
• Northbound via R650: At least 10 min before Sharm-El-Sheikh 'SHM', call South Identification 122.850
or 132.000. Maintain at or above FL120, unless cleared otherwise.

Do other countries aside from Israel have some special requirements on wearing seatbelt upon the approaching destination but before the aircraft descent?

Reddit user aries_burner_809 mentioned a similar requirement for DCA airport:

After 9/11, in the USA, the FAA implemented a 30 minute rule at DCA that mandated no standing in the plane for the first 30 mins out, and final 30 mins into the airport. DCA is inside the National Capital Region. That rule was ended.


text:
How do airlines decide whether to renumber a diverted flight, and what are the upsides of doing so?
I read on Singapore Airlines flight to Tokyo diverted to Taipei due to cracked windshield (mirror):

The flight has been renumbered to SQ9876 and will depart Taipei for Tokyo at 8.30pm. It is due to arrive at Haneda Airport at 12.30am on Tuesday, a delay of about 18 hours.

How do airlines decide whether to renumber a diverted flight, and what are the upsides of doing so?

@PeterM Deleting this question here and reposting there wouldn't migrate littleadv's answer. Also your proposed heuristic fails on many questions, e.g. many why questions.

Similar question: https://aviation.stackexchange.com/q/14382/7532


text:
What happens if an airline reports a high number of involuntary denied boardings to the Department of Transportation?
I read (mirror):

it’s in Delta’s interests to offer more in compensation for a voluntary bump rather than reporting higher involuntary denied boarding numbers to the Department of Transportation.

What happens if an airline reports a high number of involuntary denied boardings to the Department of Transportation?

Seems more like a [travel.se] question than [aviation.se]...

@FreeMan thanks, some people on travel.SE told me to ask here. I have no preferences.


text:
Can a belly landing stop more slowly than a regular landing? If so, why?
I read on the Wikipedia page about the Jeju Air Flight 2216 crash today:

The aircraft overshot the runway and struck an embankment holding the ILS array while attempting a belly landing after its front landing gear failed to deploy at Muan International Airport.

This makes me wonder, regardless of that specific incident: Can a belly landing stop more slowly than a regular landing? If so, why?
I looked at https://en.wikipedia.org/wiki/Belly_landing but didn't find any answer there.

It depends on the friction coefficient between the runway and the aircraft.
Tires (as long as they are not slipping as in a normal landing) can go somewhere from 0.5 to 0.8 (depending on the runway conditions) maximum - the real force is determined in the cockpit. In normal operations you want to break as little as possible to reduce the wear on the brakes.
This is static friction. Sliding friction will be much lesser and will vary significantly on many condition.
Metal on asphalt can be assumed in the 0.3 to 0.1 range - even less when even slightly wet.
The next problem is, this is not linear - it roughly follows a 1/x curve, so a lower braking action will significantly increase the distance required.
So it much depends on the individual situation if a belly landing has a longer or shorter distance then a normal landing.

The use of lift spoilers/air breaks/flaps influences the deceleration. The actual touch down point determines how much asphalt is available to slow down the aircraft before it slides on grass. Both factors played a role in the referenced case, but we don't know wether hydraulics power was available and where the aircraft landed.

I'm going with liquid (melted) aluminum as a lubricant.  +1 for stating a wide (and unpredictable) coefficient for belly landing.

There's also the fact that you probably don't have thrust reversers during a belly landing,  since they usually won't deploy until after the gear compress from weight landing on them (and many types of reverser would be unreliable or actively torn off in this scenario anyway).

Yes.  If the nose is held up friction drag may be reduced to a level less than "normal" brakes and reverse thrusters.
Airliner brakes can hold against the full thrust of the aircraft on a dry clean runway surface, as long as they do not overheat.  Spoilers also assist in slowing down a normal landing.

One might graph drop in friction coefficient drop with the onset on (friction) melting aluminum.  (Did you all ever see what an icecube does on a hot griddle?)

If brakes are holding the wheels stationary, there is no movement, so no friction, so no heat being generated. The tires could possibly skid, but if the brakes start out cold, they don't get hot by holding the aircraft stationary. They get hot by slowing a moving aircraft.

Well Ralph, we have now arrived at the concensus that motion heating metal (or what ever any friction brake is made out of) may start to degrade its performance (landing brakes are also "cold").  Heat generated (by the aircraft skidding on its belly or by braking) will be proportional to energy taken out of the aircraft (by slowing it).  And just as brake performance degrades when heated, so will the belly braking performance degrade --> catastrophically, when it begins to melt.  I dare say aluminum melts at a lower temperature than brake rotors.